Carney said that tail risks -- an unlikely event which could prompt a market sell off -- are "still out there."

"I got here on Thursday midday and at that point the discussion was that the tail risks had been reduced. Sometime by last evening that became: tail risks have been eliminated," he said.

Central banks alone cannot remove risk, said Carney , who takes over as governor of the Bank of England this summer.

"It's not just about central bank action. Central bank action (is) absolutely important. The LTRO (long term refinancing operations) and then the OMTs (outright monetary transactions) by the ECB (European Central Bank) (is) crucial, but not decisive," Carney said.

The key focus for monetary policy now, Carney argued, should center on achieving "escape velocity" -- or getting the major economies to take off.

He said action by the ECB had been reinforced by measures at the national level, both on the fiscal side within Europe and on the structural side. "Clearly neither of those agendas are anywhere close to being finished," he said.

The situation in the United States was similar, he said. The extraordinary actions of the Federal Reserve had been "crucial but not absolutely decisive."